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Radio-over-fiber (rof) optical fiber cable system with transponder diversity and rof wireless picocellular system using sameRadio-over-fiber (rof) optical fiber cable system with transponder diversity and rof wireless picocellular system using same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080070502, Radio-over-fiber (rof) optical fiber cable system with transponder diversity and rof wireless picocellular system using same. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]The present invention relates generally to wireless communication systems, and in particular relates to centralized optical-fiber-based wireless systems and methods employing radio-frequency (RF) transmission over optical fiber. [0003]2. Technical Background [0004]Wireless communication is rapidly growing, with ever-increasing demands for high-speed mobile data communication. As an example, so-called "wireless fidelity" or "WiFi" systems and wireless local area networks (WLANs) are being deployed in many different types of areas (coffee shops, airports, libraries, etc.). Wireless communication systems communicate with wireless devices called "clients," which must reside within the wireless range or "cell coverage area" in order to communicate with the access point device. [0005]One approach to deploying a wireless communication system involves the use of "picocells," which are radio-frequency (RF) coverage areas having a radius in the range from about a few meters up to about 20 meters. Because a picocell covers a small area, there are typically only a few users (clients) per picocell. Picocells also allow for selective wireless coverage in small regions that otherwise would have poor signal strength when covered by larger cells created by conventional base stations. [0006]In conventional wireless systems, picocells are created by and centered on a wireless access point device connected to a head-end controller. The wireless access point device includes digital information processing electronics, a RF transmitter/receiver, and an antenna operably connected to the RF transmitter/receiver. The size of a given picocell is determined by the amount of RF power transmitted by the access point device, the receiver sensitivity, antenna gain and the RF environment, as well as by the RF transmitter/receiver sensitivity of the wireless client device. Client devices usually have a fixed RF receiver sensitivity, so that the above-mentioned properties of the access point device mainly determine the picocell size. Combining a number of access point devices connected to the head-end controller creates an array of picocells that cover an area called a "picocellular coverage area." A closely packed picocellular array provides high per-user data-throughput over the picocellular coverage area. [0007]Prior art wireless systems and networks are wire-based signal distribution systems where the access point devices are treated as separate processing units linked to a central location. This makes the wireless system/network relatively complex and difficult to scale, particularly when many picocells need to cover a large region. Further, the digital information processing performed at the access point devices requires that these devices be activated and controlled by the head-end controller, which further complicates the distribution and use of numerous access point devices to produce a large picocellular coverage area. [0008]One application of picocellular wireless systems involves providing a number of different services (e.g., WLAN, voice, RFID tracking, temperature and/or light control) within a building, usually by deploying one or more optical fiber cables close to the ceiling. A problem with such cable installation is the chance of one or more transponders being obstructed by a portion of the building structure, such as metallic framework of a drop-down ceiling. The effect of such an obstruction degrades the radiation characteristics of the antenna, which reduces the ability of the picocell to properly function. [0009]Another problem is the multi-path (fading) nature of signal propagation in indoor wireless environments. This simply means that local maximas and minimas of desired signals can exist over a picocell coverage area A receiver antenna located at a maximum location will have better performance than a receiver antenna located in a minimum position. SUMMARY OF THE INVENTION [0010]One aspect of the invention is a radio-over-fiber (RoF) optical fiber cable system with transponder diversity for a RoF wireless picocellular system. The system includes at least one optical fiber cable and two or more transponders optically supported by the at least one optical fiber cable. The two or more transponders are arranged to form one or more groups of two or more proximately located transponders. The transponders in a given transponder group are adapted to form corresponding two or more substantially co-located picocells. The system also includes a diversity combiner optically coupled to each transponder. The diversity combiner is adapted to determine respective signal strengths from each transponder in each transponder group to ensure the transponder with the greatest signal strength in a given transponder group is used to form the picocell for the given group. [0011]Another aspect of the invention is a RoF wireless picocellular system. The system includes one or more RoF optical fiber cables adapted to operably support, either individually or collectively, one or more transponder groups each having two or more transponders. Each transponder is adapted to form a picocell substantially co-located with picocells formed by the other transponders in the corresponding transponder group. The system also includes a central head-end station optically coupled to the one or more RoF optical fiber cables. The central head-end station is adapted to provide downlink optical signals to each transponder and receive uplink optical signals from each transponder. The system further includes a diversity combiner operably coupled to or included in the central head-end station. The diversity combiner is adapted to receive uplink signals from each transponder to determine relative uplink signal strengths from each transponder in each transponder group, including a greatest uplink signal strength. The central head-end station then provides the downlink optical signals to the transponder in each transponder group having the greatest uplink signal strength. [0012]Another aspect of the invention is a method of providing transponder diversity in a RoF wireless picocellular system. The method includes optically supporting in one or more RoF optical fiber cables one or more transponder groups each having two or more transponders, wherein the transponders in each transponder group are arranged to form substantially co-located picocells. The method also includes determining whether a transponder in a given transponder group has a greater signal strength than the other transponders in the group. The method further includes addressing the transponder having the greater signal strength. [0013]Additional features and advantages of the invention are set forth in the detailed description that follows, and will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description that follows, the claims, as well as the appended drawings. [0014]It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and, together with the description, serve to explain the principles and operations of the invention. [0015]Accordingly, various basic electronic circuit elements and signal-conditioning components, such as bias tees, RF filters, amplifiers, power dividers, etc., are not all shown in the Figures for ease of explanation and illustration. The application of such basic electronic circuit elements and components to the systems of the present invention will be apparent to one skilled in the art. BRIEF DESCRIPTION OF THE DRAWINGS [0016]FIG. 1 is a schematic diagram of a generalized embodiment of an optical-fiber-based wireless picocellular system according to the present invention showing a head-end unit optically coupled to a transponder via an optical fiber RF communication link, along with the picocell formed by the transponder and a client device within the picocell; [0017]FIG. 2 is a detailed schematic diagram of an example embodiment of the system of FIG. 1, showing the details of the head-end unit, the optical fiber RF communication link and the transponder; [0018]FIG. 3 is a close-up view of an alternative example embodiment for the transponder of the wireless system of FIG. 2, wherein the transponder includes a transmitting antenna and a receiving antenna; [0019]FIG. 4 is a schematic diagram of an example embodiment of an optical-fiber-based wireless picocellular system according to the present invention that utilizes a central head-end station and multiple transponders arranged along an optical fiber cable; [0020]FIG. 5 is a detailed schematic diagram of an example embodiment of the central head-end station of the system of FIG. 4; [0021]FIG. 6A is a close-up cut-away view of the optical fiber cable of the system of FIG. 4, showing two transponders, the downlink and uplink optical fibers, and the electrical power line that powers the transponders; Continue reading about Radio-over-fiber (rof) optical fiber cable system with transponder diversity and rof wireless picocellular system using same... Full patent description for Radio-over-fiber (rof) optical fiber cable system with transponder diversity and rof wireless picocellular system using same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Radio-over-fiber (rof) optical fiber cable system with transponder diversity and rof wireless picocellular system using same patent application. 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A digital copy of content of the electronic whiteboard is received at the portable electronic device over the established ... ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Radio-over-fiber (rof) optical fiber cable system with transponder diversity and rof wireless picocellular system using same or other areas of interest. ### Previous Patent Application: Pairing of wireless devices using a wired medium Next Patent Application: Portable electronic device and a method in a portable electronic device Industry Class: Telecommunications ### FreshPatents.com Support Thank you for viewing the Radio-over-fiber (rof) optical fiber cable system with transponder diversity and rof wireless picocellular system using same patent info. 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